net: airoha: fix BQL underflow in shared QDMA TX ring

When multiple netdevs share a QDMA TX ring and one device is stopped,
netdev_tx_reset_subqueue() zeroes that device's BQL counters while its
pending skbs remain in the shared HW TX ring. When NAPI later completes
those skbs via netdev_tx_completed_queue(), the already-zeroed
dql->num_queued counter underflows.

Fix the issue:
- Remove netdev_tx_reset_subqueue() from airoha_dev_stop() so pending
  skbs are completed naturally by NAPI with proper BQL accounting.
- Rework airoha_qdma_tx_cleanup() to disable TX DMA, flush BQL
  counters, DMA-unmap and free all pending skbs while skb->dev
  references are still valid. Use a per-queue flushing flag checked
  under q->lock in airoha_dev_xmit() to prevent races between teardown
  and transmit. Call airoha_qdma_stop_napi() before
  airoha_qdma_tx_cleanup() at the call sites.
- Move DMA engine start into probe. Split DMA teardown so TX DMA is
  disabled in airoha_qdma_tx_cleanup() and RX DMA in
  airoha_qdma_cleanup().
- Remove qdma->users counter since DMA lifetime is now tied to
  probe/cleanup rather than per-netdev open/stop.

Fixes: a9c2ca61fec7 ("net: airoha: Support multiple net_devices for a single FE GDM port")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260620-airoha-bql-fixes-v3-1-76b95374e63e@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions